Intelligent video surveillance technology is widely used. By placing a plurality of cooperative cameras and using image processing, this technology may be used for space detection in a large area, such as parking space detection.
The parking space management usually relies on manual registration, using mechanical bar at the entrance, or installing sensor at each parking space to register the space status. Although the parking management has a simple structure, to find a parking space in a large outdoor parking lot, such as shopping mall, stadium, theater and office building, still takes a lot of time. The registration at the entrance may only provide the number of available parking spaces instead of the exact location of the available space. It is not only inefficient, but also fails to provide other valuable service functions, such as surveillance, guided parking, and so on.
The use of sensors, such as infrared, supersonic, electromagnetic, at each parking space requires the installation of the sensor, which may be prohibitively expensive for a large parking lot. In addition, the maintenance is costly, and may also be affected by the temperature, humidity or other climatic factors. This type of parking space management provides no further safety integrated services, such as guided parking, car surveillance, car theft prevention, bumping tracking, and so on.
The parking management technology is usually classified as sensing-based parking management detection technology or mechanical control based parking management detection technology. The sensing-based technology uses a sensor, such as parking card sensor, infrared sensor, supersonic sensor or electromagnetic sensor. The operation theory is to use a microwave transmitter to transmit microwave (infrared/supersonic) to detect whether a parking space has any large object responding to the microwave, such as blocking or reflecting the microwave. A receiver determines whether a corresponding signal is received to detect the presence of a vehicle. As the sensor may only detect a limited area, each parking space must have its own detection unit. Hence, the high set-up cost, complex hardware wire and difficult maintenance all contribute to the unpopularity of this technology.
Mechanical control based technology uses mechanical facility, such as raising bar, to control and record the number of the cars entering and leaving, and the number of the parking spaces. However, a mechanical bar at the entrance only counts the number of the cars inside the parking lot to get a rough estimation of the available space, but is unable to detect the status of individual parking space and finding the exact location of the available parking space. Hence, finding available parking space may take much time. To alleviate the above problem, a mechanical bar may be installed at each parking space; however, this again involves a high set-up cost. This solution may only be suitable for small parking lots.
U.S. Pat. No. 6,694,259 disclosed a system and method for delivering parking information to motorists. An exemplary embodiment is to use image analysis to find available parking space. By comparing the grey-level values of the image taken by the camera with an unoccupied parking space model, the system may detect whether the parking space is unoccupied. However, the disadvantage is that the precision of this method may be affected by the light and the climate change, or by the camera angle and the shielding of nearby cars.
U.S. Patent Application No. 2003/0144890 disclosed a parking management system and method, where the system user may reserve or bid on a parking space, or join a loyalty program to use the parking management system. An exemplary embodiment of this patent application is to encode all the pixels of an image of a single parking space taken by a camera into a feature vector, and then divide as unoccupied or occupied status to realize the space detection. This method has the disadvantage that the pixel coding can be affected by the light change or noise interference. Another exemplary embodiment uses the detection of the presence of license plate in a parking space as the basis for determining whether the space is occupied or unoccupied. This embodiment also has the disadvantage of the camera angle, the possible incompleteness of a license plate image and the shielding by nearby cars.